In optical communication, an important role is played by an optical transceiver for transmitting and receiving an optical signal, and an optical fiber serving as a medium for transmission of the optical signal, respectively. An optical semiconductor device for converting an electric signal into an optical signal, and vice versa, and a printed wiring board with electronic elements for control, electrical connectors, and so forth, mounted thereon, are encased in a box of an optical transceiver.
Typical embodiments of an optical semiconductor device are disclosed in Japanese Patent Application Laid-Open Publication No. 2007-43496, Japanese Patent Application Laid-Open Publication No. 2007-42756, Japanese Patent Application Laid-Open Publication NO. 2006-80418, and so forth, respectively. The optical semiconductor device is comprised of a CAN type optical package with optical elements capable of optic-electronic conversion, such as a laser (light transmission element), and a photodiode (light-sensitive element), mounted therein, and a flexible substrate. Such a makeup of the optical semiconductor device is often used in an optical transceiver capable of coping with a transmission speed in a range of about several hundred Mbps to 10 Gbps.
According to conventional examples described as above, the following method is adopted as a method for joining the CAN type optical package with the flexible substrate. It is a method whereby the flexible substrate having holes is fitted over lead pins protruding from the rear surface of the CAN type optical package, and the lead pins each are fixedly attached to part of the flexible substrate, around each of the holes. As is so often the case, the lead pins each are generally a terminal for grounding, power supply, and signal, and the lead pins are fixedly attached to a metal pattern provided on the flexible substrate, ensuring electrically continuity therebetween by soldering. Since the lead pins of the CAN type optical package are inserted in the holes of the flexible substrate, respectively, connection therebetween is solid, and highly resistant to stress due to a change in temperature and humidity, and mechanical pressure, so that the optical semiconductor device has the advantage in that its reliability as a product is high.